The present invention generally relates to cooling systems. More particularly, this invention relates to a cooling system suitable for providing a cooling fluid to a blast furnace during operation.
Water is the typical cooling fluid used by cooling systems within blast furnaces, for example, of types used in iron-making processes. During the life of a blast furnace, passages within the cooling system that deliver the cooling fluid to the blast furnace may deteriorate and/or become damaged, thereby allowing water to leak from the system into the high temperature process within the furnace. A leak in the cooling system changes the dynamics of the cooling system, impacts the reaction in the furnace, and decreases the performance and efficiency of the furnace. Moreover, if the leak is not detected in a timely manner and water is injected into the furnace, hydrogen is produced resulting in dangerous safety conditions and causing erosion in the furnace walls, dome, and hearth that can be expensive and time consuming to repair. Therefore, when a leak occurs in the cooling system, water can most likely no longer be used as the cooling medium in the cooling system. However, cooling must to be restored to prolong the furnace life.
In view of the above, once a leak has been detected in a cooling system for a blast furnace, the cooling system must be promptly replaced, repaired, or modified or an alternative cooling fluid must be used. One approach to repair or modify a cooling system is to insert a small diameter metallic hose into the passage where a leak has occurred, and then fill the annular gap between the hose and the surrounding passage with grout. Water can then once again be used as the cooling fluid. However, the grout is often much more insulating than the original passage walls, with the result that effective cooling may be compromised. In addition, the time to install the hose and grout the gap between the hose and passage may require an extended outage of the blast furnace. In addition, the diameter of the hose is less than the original passages and therefore restricts the quantity of water that can be used for cooling. As a result, the heat removal capacity within the blast furnace is likely reduced.
Another approach is to use dry nitrogen in place of water as the cooling media. Dry nitrogen is used because it is readily available and has minimal effect on the blast furnace process even if some of the nitrogen leaks into the furnace process. However, nitrogen has a limited cooling effectiveness due to its very low heat capacity. Therefore, as with the previous cooling system repair, the heat removal capacity within the blast furnace is likely reduced.
A cooling system commercially available under the name CIM-Cooler, produced by CIM-Tech, Inc., has provided an alternative approach wherein the cooling water is replaced with a nitrogen mist comprising nitrogen mixed with atomized water. The nitrogen mist has significantly greater heat removal capacity relative to dry nitrogen. While this system provides significant improvements over the two previously described approaches, spray nozzles used by the system to atomize water may become plugged or damaged, necessitating that the blast furnace be taken offline in order to repair or replace the spray nozzles.
In view of the above, it can be appreciated that there is a desire for cooling systems that are capable of delivering a cooling fluid to a blast furnace during operation that has a heat removal capacity comparable to water-based cooling systems, but can be repaired without taking the blast furnace offline.